The present invention relates to an apparatus for operating a high-pressure discharge lamp and, more particularly, to an apparatus comprising a heater for heating a high-pressure discharge lamp and a battery for supplying power to the lamp and the heater.
A high-pressure discharge lamp has a light-emitting tube filled with a starting rare gas such as mercury or metal halide. A high-voltage pulse is applied to the lamp, whereby the light-emitting tube emits light. The output luminous flux of the lamp increases slowly, however since the mercury or metal halide sealed in the tube has not sufficiently evaporated. It usually takes the luminous flux several minutes to reach a desired value. To solve this problem, a heater can be used to heat the light-emitting tube. When the tube is heated, the mercury or metal halide will quickly evaporate, whereby the luminous flux increases fast upon starting the lamp.
Conventional, high-pressure discharge lamps have been made smaller and smaller, and they are now used as battery-driven portable lamp units such as a video light and an automobile head light. However, when a heater is used in such a battery-driven portable lamp unit to heat the light-emitting tube, the battery voltage is lowered very soon since the heater consumes much power. Once the battery voltage has fallen too much, the discharge lamp can no longer remain on.